Get the list of devices registered on the user's account.

💾 This method alters the persisted account state.

This method returns a list of `Device` structs representing all the devices currently attached to the user's account (including the current device). The application might use this information to e.g. display a list of appropriate send-tab targets.

Arguments

- `ignore_cache` - if true, always hit the server for fresh profile information.

Notes

- Device metadata is only visible to applications that have been
  granted the `https:///identity.mozilla.com/apps/oldsync` scope.